In the area of semiconductor memory devices such as semiconductor memory products and semiconductor-memory-equipped logic products, when analyzing a defective cell, it is necessary to identify the location of the defective cell on an actual chip based on the defective bit address detected by a tester and to process a sample with an FIB (Focused Ion Beam) analysis method for observation with an SEM (Scanning Electron Microscope), a TEM (Transmission Electron Microscope), or the like.
Conventionally, in order to identify the location of a target defective cell, the chip needs to be polished until a layer in which 1-bit memory cells are recognizable, and marks need to be provided every few cells using the FIB analysis method to count memory cells without missing a single cell. Thus, a large number of processing seps are needed to process the sample, and it takes time to identify the location of the defective cell, possibly resulting in misidentification of the location of the defective cell.
Patent Document 1 discloses a semiconductor memory device comprising a chip on which memory cells are arranged in the form of a matrix. This document discloses that array marks made of two material layers as markers are used to indicate the arraying sequence of the memory cells, and it also discloses that a target memory cell can be identified by counting the array marks (conventional example 1).
Also, Patent Document 2 discloses a semiconductor memory device comprising a substrate on which memory cells are arranged in a repetitive pattern, a protective film formed above wiring layers relating to the memory cells, and optically recognizable film patterns located in the protective film, each pattern being located at a place corresponding to each of the memory cells. This document discloses that, by using the above film patterns and providing predetermined areas of the protective film with marks, the location of a target memory cell at least corresponding to a predetermined address used as information is recognized (conventional example 2).
Patent Document 1: Japanese Patent Kokai Publication JP-H3 (1991)-165556-A (FIG. 1)
Patent Document 2: Japanese Patent Kokai Publication JP-2003-68986-A (FIG. 1)